Control system



G. E. KING CONTROL SYSTEM Nov. 12, 1940.

Filed March 30,- 1938 2 Sheets-Sheet 1 4 a \6 w w H 2 f. 5 Q 9 w 5 l 4) 0 9 w 3 a\ =1 I F m y n w 2 u v 4 z R n I 2 M 5 9 4J2 2 Z o 1/ 1 11. v 7 5 4 6 3 3 9 a 3 v l m= 5 R i 2 i? 5 w H 6/ m INVENTOR George E King.

ATTORNEY Nov. 12, 1940. G. E. KlNG 2,221,584

CONTROL SYSTEM Filed March 30, 1938 2 Sheets-Sheet 2 INVENTOR 66023029 Z. WM? 552M ATTORNEY operation generates a corrective voltage.

Patented Nov. 12, 1940 UNITED- STATES.

raran'r OFFICE CONTROL SYSTEM George E. King, Wilkinsburg, Pa", assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa, a corporation of Pennsylvania Application March 30, 1938, Serial No. 198,883

3 Claims. (Cl. -2

motors used to drive reciprocating mechanisms; such as elements of planers, draw-cut shapers, or

roll grinders, transfer tables, etc., by a variablevoltage control.

In a conventional variable-voltage control, the motor is ordinarily provided with a separately excited field winding and the desired direction of rotation of the motor is effected by reversing the polarity of the energy supplied to the motor armature. The motor is arranged to be energized from a generator which may be provided with a series field winding to compensate for the IR drop in: the generator armature circuit; the armature circuit of the motor; the series field winding itself; and the leads interconnecting the generator and motor armatures. The generator is provided with a separately excited main field winding, the current through which isarranged to be controlled and reversed in order to operate the motor and the load attached thereto, for example a planer platen, at various speeds in either direction of travel. The excitation of the main field Winding of the generator may be controlled by means of a rheostat or the combination of various resistors and suitable control devices for inserting various steps of resistance in circuit with the main field winding. For each position of the controller controlling the field current in the generator, there is a particular speed of operation of the motor and thus the load, as a planer platen, that is desired. Any departure in speed from the desired value introduces undesirable operations of the load. If it were possibleto maintain all of the conditions affecting such a control constant the desired operation could be secured.

with the simple conventional variable-voltage control ,just briefly explained.

Since it is impossible to maintain the conditions ailecting a variable-voltage control constant I use, with such control, a regulator-generator having a series field winding l4 arranged to be responsive to the current supplied to the motor, a main or shunt field winding arranged to be responsive to the voltage applied to the motor and a field winding responsive to the excitation current of the shunt field winding of the generator to be controlled. These field windings are so disposed that the regulator-generator in The armature of the regulator-generator is connected in series circuit relation with, one field winding of the regulator-generator, the field winding of the generator of the variable-voltage system, and -to the controller, which controller may be operated to independently vary the flow of current f'through the main generator field winding.

By a proper selection of the electrical characteristics and constants of the electrical units included with the variable-voltage control I have devisedfa'nd by making some minor compromises, the desired functioning can be secured, that is, the motor speed can be made proportional to the setting of the controller regardless of variations in load on the motor; direction of operation of the motor; variations in ambient temperature; and regardless of the many other factors that would ordinarily prevent the desired operation of the-motor.

One object of my invention is to provide a con stant speed for a tool operating machine regardless of the variations in load on the machine.

A broad object of my invention is to provide a control for anelectrically operated tool operating machine so as to cause said machine to operate at any selected constant speed for any selected direction of operation regardless of the variable characteristics of the system.

Another object of my invention is to provide for constant speed of operation of a tool operating machine, through electrical means, regardless of load variations on the machine that vary from full load overhauling through zero to full load.

A still further object of my invention is to automatically and invariably secure the same operation of a machine for a given control position of a controller for the machine regardless of any other forces, than those set in operation by the controller, that might influence the operation of the machine.

It is also an object of my invention to provide for any selected constant speed of operation for either direction of operation of a reciprocating machine.

A more specific object of my invention is to provide for so controlling a reversible motor, op erating a machine tool, as a planer platen, a roll table,;etc., so as to provide any selected constant speed of operation for the machine for one direction of operation of the motor and to provide any selected constant speed of operation for the machine for another direction of operation of the motor.

It is also a general object of my invention to provide a control system for a tool operating machine that shall be simple, efficient and accurate in operation, and which may be readily and economically manufactured and installed.

Other objects and advantages will become more apparent from a study of the following specification when considered in conjunction with the accompanying drawings, in which:

Fig. 1 is a diagrammatic representation of a system of control for a reversible motor operating a planer platen or other tool actuating machine;

Fig. 2 is a side view, somewhat diagrammatic, of a planer having a tool support and having a motor for operating the platen;

Fig. 3 is a plan view of the subject matter shown in Fig. 2; and

Fig. 4 is an elemental circuit diagram of that portion of my system of control separated from the machine with which it is to coact.

In the practice of my invention, I provide a variable-voltage control in which the motor M is mechanically coupled to drive a machine tool, as a planer platen I. The motor M is provided with a separately excited field winding 2 which is arranged to be energized in a single direction only. A generator G is provided having its armature 3 substantially directly connected to the motor armature 4. The control of the speed of the motor, and in consequence the planer platen and the direction of movement of the planer platen is efiected by varying the amountand direction oi excitation of the field winding 5 of the main generator. This controlmay be eflected in a few steps or in many steps, depending upon the type of operation that is desired.

In order to maintain the speed of the motor M at various constant values corresponding to various settings of the controller 8 used for controlling the current flowing through the main field winding 5 of the generator, a regulator- .generator R is provided which is arranged to measure the speed and load of the motor and the current flowing through themain field winding 5 of the generator. The armature 9 of the regulator-generator is arranged so that it may be connected in series circuit relation with the generator field winding 5, whereby the voltage generated in the armature 3, in response to the speed and load of the motor and the current flowing through the generator field winding, will cause a current to flow through the main generator field winding 5, which current will be a function of the departure of the motor speed from a predetermined value corresponding to the particular setting of the controller I for the main field winding, that is, corresponding to the adjustment oi lead Iii-on the rheostat l2.

Under certain load and operating conditions, no voltage will be generaltedinthe armature 9 of the regulator-generator R since under these conditions. the speed of the motor M corresponds to the setting of the controller 8. For all other conditions, however, a voltage will be generated in the armature oi the regulator-generator in such direction and of such a value as to cause the required current to flow through the main field winding 5 of the generator G to operate the motor M at the desired speed.

In order to measure the speed and load applied to the motor M, the regulator-generator is provided with a series fleld winding ll through which all or a portion of the current flowing from the generator G to the motor M flows. The regulator-generator is also provided with a main field winding l5 which is connected to be responsive to the voltage applied to the motor M. This winding l5 may also be designated a shunt field winding since it is shunted acros the generator armature 3. These two field windings, namely I and I5, are differentially related to each other so that the resulting magneto-motive force is a function of the speed of the motor, as measured by the counter-electro-motive-force of the motor M, that is, the magneto-motive force produced by the series field winding H is proportional to the IR drop of the motor armature 4, and the magneto-motive force produced by the main field winding ii of the regulator-generator is proportional to the voltage impressed across the terminals of the armature of the motor. Thus, the resulting magneto-motive force due to the difierential relationship between the two field windings (considering these fields only), is a function of the counter-electro-motive-force of the motor. Since this magneto-motive force results from the combined action of the current flowing through the motor armature and the voltage applied thereto, it is also a function of the load carried by the motor. The voltage which is generated in the armature of the regulator-generator, due to this resulting magneto-motive iorce, is then a function of the speed of the motor and the load carried thereby.

It is desirable that any change caused in the excitation of main generator caused by the voltage generated in the regulator-generator armature and affecting the current flowing through the main field winding 5 of the generator G be immediately reflected in the voltage generated in the armature 9 of the regulator-generator R. Such action is desired in order to prevent hunting of the system. As soon as a voltage appears in the armature of the regulator-generator, indicating that the speed of the motor M has departed from the desired speed, a change in the flow of current through the main field winding 5 of the generator G takes place in such direction as to tend to restore the speed of the motor to the desired speed. If'some means is not provided for immediately effecting a corresponding change in the corrective voltage generated in the armature 8 of the regulator-generator R, the resulting change in the fluxes of the series and main field windings I 4 and I5, respectively, of the regulator-generator in response to the corrective effeet, will take place too late. As a result, the speed of the motor will be altered more than is desired and hunting will result.

In order to make the correction applied by the regulator-generator proportional to the departure of the speed of the motor from the desired speed corresponding to a particular setting of the controller for the main field winding 5 of the generator G, a differential field winding I8 is provided in the regulator-generator. This field winding II is connected in series circuit relation with the main field winding 5 of the generator G. Thus, any changein current which flows through the main generator field winding 5 is immediately reflected in the voltage which is generated by the armature of the regulator-generator. It is then unnecessary to await the correction in the speed of the motor, as reflected in the change in the magneto-motive forces produced by the series and main field windings of the regulatorgenerator to correspondingly affect the voltage generated by the armature of the regulator-generator. The differential field winding 16 of the regulator-generator is arranged to produce a magneto-motive force in the same direction as the magneto-motive force produced by the series field winding ll of the regulator-generator and, therefore, it opposes or is differentially related to the magneto-motive force produced by the Ell d ll

accuses main field winding l5 of the regulator-generator. There is always, then, a certain relationship he tween the speed and load or the motor and the corrective efiect caused thereby in altering the how or current through the main field winding oi the generator. As a. result, the system is free from hunting and the speed of the motor is maintained at predetermined values correspond ing to various settings of the lead it of the con troller it regardless oi variable conditions wh ch would otherwise affect the speed and cause it to change from the desired value.

he has been stated hereinbeiore, it

able to effect a corrective action in the cur t flowing through the main field winding 5 cl e generator G by means of the regulator-genera the motor.

l have discovered that a Wheatstone arrangement may be combined with com for machine tools to effect the desired inde out control of the current flowing through t main field Winding E5 of the generator vide a balanced Wheatstone bridge cnrcult which the differential field Winding id of a regulator-generator and the main generator fi d winding ii are connected in series role and form a part or all of one of the branches c the bridge circuit. The armature oi the later-generator is connected across one pi .i opposite terminals of: the Wheatstone b idge ctr cult while the remaining pair of i 1 netted through some switches throw.

M designates generally the motor mechanically coupled to drive the planer platen l of the planer IS. A work piece I9 is shown mounted on the platen and as the platen reciprocates by reason of the reversing operation of the motor ;.-M the tool 20 mounted on a cross rail, not shown, operates on the work piece IS.

The motor is substantially directly electrically connected to the, generator G. The generator G has a main field winding 5 and a diflerential stabilizing field winding 2|. The armature 3 of the generator G is mechanically coupled to the shaft 22 of the induction motor, or other prime mover, P. This induction motor P is disposed to be connected to the buses 23, 24 and 25, leading to a suitable source of alternating current energy.

In order that I may control the functioning of the system in the manner desired, I utilize a regulator-generator which regulator-generator has the armature 9 mechanically coupled to an induction motor 26.-

Motor 26 is provided to drive theregulator-generator at a relativelyconstant speed. The regulator-generator may be operated at the same speed as the generator G. In practice, since generally designated R,

it that they produce magneto i of either the reversing con the commotion the controller 8 control.

l in ancth tional contac or 8i one is to independently con e ilel generator 31- ir two sources, o.

co prising the exciter E css t matu e For: purpose,

o, Whcatstone To the custom my four the l opposite to circuit while the oridge are con the octet and res "3.7 and st" ltches o the directional contactors 8G til to exclter The series field wind it of the regulator-generator is connected, as hlustrated, in series circuit relation with an adrlustable resistor R5 disposed in the ch'cuit con necting the armatures El and oi the generator (El and motor M, respectively. An adjustable shunt 2?! may be provided for adjusting the flow of current through the series field winding it. The shunt field winding it of the regulator-genorator is connected through an adjustable resistor RB across the armature terminals of the motor M. The resistor R6 is used to reduce the heat loss in the main field winding l5, and in consequence reduces to a minimum any change in resistance oi the field winding It by reason of temperature changes.

To analyze the functioning of the Wheatstone 'loridge and the regulator-generator, an investigation of the mathematical relations oi the circult characteristics may not be amiss,

Let V:the control voltage that may be obtained from the controller 8, that is, the voltage from junction 90 to junction 9|.

Let the four branches of the Wheatstone bridge be indicated by the resistors R1, R R and R4. Thearesistor R3 is, oi course, composed of the resistance value of the differential field winding IQ of the regulator-generator R and the main fleld winding 5 of the generator G. It may in '16 the adjustable resistor in connected in series with the main field winding I I.

v=I.R1 +1.12 nd II- Solving in (4) for I: from (1), (2) and (3),

Simplifying, then Since in a Wl-ieatstone bridge the following relation R1R4=R2Rz is true then by substituting in (6; and iurther simpliiying I obtain Equation 7 will apparent that either the control voltage V, or the regulate? vol re ER may he changed to independently prochanges in the current 1: flowing through,

winding 5 of the gererato'r G. :as been hereinbei'ore lxnnted out, it is deelra'r-le to maintain a predetermined relationship between the speed 01 the motor M and the com t-l'Ol voltage V represented by the setting of the lead 68, of the controller 8, regardless of the variable characteristics oi the system or the .1 of rotation oi the rs rtor M. The relyenerator P. serves as an automatic cornremit-iii: K effect this desired relationships the regmator'generntur is used there is r. :rnstani relation between the speed of the B2222! In, and the control voltage V, which relemon, due to the regulatormeneratcr R, is on reflected by the variable characteristics of the system. That this relationship is true will be apparent iron-i the following:

The voltages generated by the regulator-senerewr. when the held windings are individually excited, may be represented by the following 75 equations:

(8) Voltage resulting from the excited dinerential field winding. ll, Eu=kuhsi (9) Voltage resulting from the excited shimt or main field winding, ll, Its-hulls;

(10) Voltage resulting from the excited series field winding, l4, Eu=kulm where he is the current in winding l8, Iuisthe current in winding II, and? is the current in winding I4, and he. he, and k1 are constants obtained from the magnetiaation curves of the regulator-generator B, when it is individually excited by the respective field windings.

The voltage En generated by the armature o! the regulator-generator equals the sum 0! the individual voltages generated by the three fleld windings when they are simultaneously energized. Since the elect of winding II is opposite to the effect of windings I4 and II,

(11) Ea=krsl1o kislu+hdu Since I1s=ls Equation 7 may be rewritten (12) 21-11mm.) g??? u u =m+ n n The current flowing through the main or shunt field winding ll of the regulatorgenerator It may be expressed by the following equation:

.anl lewhere E; represents the voltage 0! generator G.

Substituting in 13)- I obtain the following =4; of the regulator series 4 and f current flowing wl diny 1&- is also negligithe rinrre: fo -121;, to the n y be neglected l Le? electrmmotive iL-rce oi. the motor x2 may be represented:

e e,- e

anneal; 1 M U the system.

A still better understanding of my system of control may be had from a more detailed study of its operation.

If the attendant wishes to start the system, he

depresses pushbutton switch 85 whereby a circuit is established from the bus 25 through switch 85, actuating coil 34 of the line switch, or contactor 35, stop pushbutton switch 41 to the bus 24. Operation of contacinr 35 causes the closing of switches 3s, 31, as, as and 40. The closure of switches es,

31, and 38 causes the energization of motors P and 26. Regulator-generator R, the main generator G, and exciter E are thus caused to operate. Closure of switch 39 establishes a holding circuit for coil 34, whereas the closure of switch 45 sets up a circuit connection to be described later.

When the motors P and 26 are up to speed, the machine l8 may be started. The exciter E will at such time generate normal voltage to thus place a predetermined potential or voltage across buses 4| and 42.

Energization of buses 4| and 42 provides energization for the neutralizing coil 48 of the time 8:) limit relay 44. The circuit for this coil may be traced from bus 4| through conductor 45, coil 48, resistor 46 to the bus 42. The effect of coil 43 may be adjusted by adjustable resistor 41.

The field winding 2 of the motor M is also energized by the energlzation of buses 4| and 42.

40 The circuit for this field may be traced from bus 4| through conductor 48, the field rheostat comprising theresistor l5 and adjustable lead it, conductor 49, through field winding 2 to bus 82 and also through the contact members 84, of accelerating control relay 85, shunting the field rheostat. An additional circuit for the motor field is also established from bus 4| through conductor 56, contact members, or switch 51. 00111- ductor 58, the controller 8, conductor 48, field winding 2 to bus 42.

A still further circuit is established from bus 4| through conductor 59, actuating coil 68 of gen-= erator stabilizing field control relay 6|, contact 55 members 62 of time limit relay 44, contact members 63 of control relay 55, and conductor 64 to bus 42. Operation of relay 6| establishes a cir-= cuit from the. upper armature terminal of the generator G through conductors 65 and 66, con= 60 tact members 61, conductor 68, generator stabilizing field winding 2| to the lower armature terminal of the generator G. Since the generator G is not generating any material voltage, motor M will not operate. i

To effect normal operation either one of the switches 28 or 29 should be operated. Let switch 28 be the forward control pushbutton switch. To efiect forward operation, that is', an operation in the out direction, the attendant depresses the 7.0 switch 28. A circuit is immediately established from bus 4| through conductor 45, the magnetizing coil 50 of the time limit switch 44, conductor 5|, reversing limit switch 52, reverse starting pushbutton switch 25, the lower terminals of 75 switch 28, switch 88, stop switch 58 and actuating coil 54 of the regulator-generatorcontrol relay 55 to the bus 42. Time limit relay 44 has a very negligible time constant when coil 50 is energized with the result that contact members 62 open immediately, whereupon coil 60 is deenergized and contact members 61 open the circuit for the stabilizing field winding 2|.

Operation of relay 55 establishes a holding circuit for itself through resistor 69 and contact members 18 and 48. Relay 55 closes switch 1| whereupon a circuit is established from energized conductor 5|, through limit switch 52, switch 28, contact members 1| and 12, actuating coil 18 of the forward directional contactor 3| to the bus 42.

The relay 55 also opens switches 51, 63 and 14. Switch, or contact members, 51 opens one of the parallel circuits for the field winding 2, namely, the circuit including the upper portion of the controller 8. The opening of switch 63 makes doubly certain that coil 68.115 not energized after the generator operates normally. Opening of switch 14 eliminates the inching push buttons 15 and 16 for inching control.

The operation of relay 55 also causes the closing of contact members 32, 11, 18 and 19. Closure of contact members 32 inserts the armature 9 of the regulator-generator R in the control system. Closure of contact members 11 shunts resistor R7 so that the voltage V across the junctions 80 and 5| of the Wheatstone bridge will principally be a function of the position of lead l8 on the rheostat |2.

Closure of switch, or contact members, 1 I, from the circuit previously traced, causes the operation of forward directional contactor 3| which contactor causes the opening of contact members 88, so that the closure of contact members 18 will have no effect, and causes the closure of contact members 88, all and 82. Closure of contact members 82 assures a strong energization of the field winding 2 even though contact members 84 open by reason of the energization of coil 86 of the re lay 85 by the closure of contact members 18. Motor M will thus have a slow cutting speed and have a high torque.

Closure of contact members 88 and 8| establishes a circuit irom bus 4| through conductor 48, adjustable lead to, a portion of the resistor oi rheostat l2, conductor 68, contact members 88, conductor 88, contact members 11 to junction 88 oi the Wheatstone bridge heretofore analyzed, through the Wheatstone bridge to the junction 6|, conductor 92, and contact members 6i to the bus 42. The regulator-generator R. connected in theWheatstone bridge having the relative circuit constants hereinbeiore specified and excited in the manner hereinbeifore specified will thus pro= duce a control eflect so as to give the planer platen a speed in the cut direction which is a direct function of the position of lead Ill on the rheo-.- stat |2. Neither the cutting load, the ambient temperature, the temperature of the electric units, nor any other of the many factors that might otherwise aflect the speed of operation of the motor M will have any material eflect. The speed of motor M will be determined by the posi-' tion of the controller lever, that is, the adjustment oi leads l8 and ti.

As the planer platen moves to the end of its stroke, a dog schematically indicated by the block 55 mounted on the platen actuates the lever 54 to open the switch 52. Coils 58 and 15 are thus deenergized. Contact members 88, 8| and 82 open and contact members 83 close.

Since the voltage oi the generator G becomes Closure oi contact members It causes the energization oi coil I! with the result that contact members it and I1 close to reverse the polarity oi the generator 6. The circuit ior the generator field winding I may now be traced irom bus 4|, conductor Bl, contact members .1, conductor 82 to Junction ll, the Wheatstone bridge including the field winding I, the junction 00, contact members 11, conductor '8, contact members II, and conductor 04 to bus 42. It will be noted that the controller is not used and that the iull voltage oi buses ll and I! is applied to the Wheatstone bridge. This arrangement assures a higher voltage of the generator during the return stroke and thus a higher speed oi the motor M.

As soon as the voltage oi the generator (3 builds up to a sufilcient value the field excitation oi the motor field 2 is decreased to thus iurther increase the motor speed. This is accomplished through the relay 8|. The reenergiaation of coil as causes the opening of contact members 84 whereupon a portion oi the resistor II is inserted in the circuit oi the field winding;

As the motor M reverses dog 03 operates back to the position shown to thus set up the connection ior the cut operation which is set up at the end oi the return stroke when the dog ll. operates lever III to open switch lltto deenergize the coil I.

The instant the return or reverse contactor SI drops coil II is energised and contact members I! closed to give a'strong field to motor I and dog Ill resets switch lOlto the position shown.

I am, oi course, awarethat otheraparticularly aiter having'the benefit oi the teachings oi my 40 invention, may devise other circuit diagrams for accomplishing the novel results I have herein disclosed,butIdo notwishto belimitedtothe particular embodiment oi my invention herein disclosed, but wish to be limited only by the scope as oi the claims hereto appended and by such prior art as may be pertinent.

I claim as my invention: 1. In a system or control ior controlling the speed of operation oi a planer pl t n. in combination, a reciprocable planer platen, a directcurrent motor ior reciprocating the platen, a direct-' current generator having its armature connected in series with the motor armature, a field winding ior the generator including in its circuit a as constant voltage exciter, reversing switches ior reversing the generator field, electromagnetic means operable by the planer platen adapted to automatically eilect the operation oi the reversing switches, a controller, a regulating-generator goconnectedinthecircuit'aoaanottohave any efi'ect on the voltage of the constant voltage exciter but whose efi'ect on the generator field niay beeitheradditiveorsuhtractivetothe eflectoi the exciter voltage as modified by the controller. osandcircuitsiorcontmliingtb operativeeii ct oi the regulator-generator and whose characteristics are so selected that the speed oi the motor is substantially entirelya iunction oi the controller operation only.

2. In a control iorsa machine. in combination. 6

a reciprocating planer platen, a reversible di rect-current motor ior reciprocating the platen, a generator connected to energize the motor, reversing and speed control means ior controlling the voltage applied to the motor and ior controll0 ling the excitation oi the motor to eiiect a rapid change oi speed oi the member irom a given full speedinonedirectiontoagiveniullspeedinanother direction, and means operable by the planer platen adapted to automatically eiiect the operation oi said reversing and speed control means. a field winding ior said generator, regulating means ior counteracting the eilect oi variables on the normal speed, in contradistinction irom the reversing speed, oi the motor, said regulating means comprising means ior producing an eiiect on said generator field winding dependent on the voltage oi the generator supplying energy to the motor, means serially connected with said generator field winding ior producing an eiiect on u the generator field winding dependent on the current in said generator field winding, and means ior producing a still iurther eiiect in said field winding responsive to the load current oi said motor which modifies said first two eiiects, co'ntrol means ior varying the component oi excitation oi said generator independently oi the operating characteristics oi said motor and said senerator and means ior preventing interchange oi energy between said regulating means and said a control means.

3. In a system oi control ior controlling the operation oi a machine tool, in combination, a member and a tool adapted to operate on a work piece, a direct-current motor ior causing relaa0 tive movement oi the member and tool to thus eiiect shaping oi the work piece, a direct-current gmerator having its armature connected in series with the motor armature, a field winding ior the generator including in itscircuit an exes circuitsiorcontrollingtheoperativeeiieetoithe so regulator-generator and whose characterlstiu aresoselectedthat'thespesdoithsmotoris substantiallyentirelyaiunetimoithecontrolla operation o ciloml n. me. as 

